An Apple spokeperson told CNET they are well aware of the security exploit found in iOS and they are apparently already working on it:

We’re aware of this reported issue, we have already developed a fix and it will be available to customers in an upcoming software update.

This security glitch found in the way iOS handles PDF documents allowed the Dev Team to create JailbreakMe, which uses this exploit to inject the jailbreak code in your iPhone. Some security experts were quick to realize that this exploit could be used to inject malicious softwares in your iDevices and brought up this issue to the general public. The jailbreak community quickly developed a fix for it which can be downloaded directly from Cydia.

This morning I highlighted the irony of the situation. Apple has always claimed jailbreaking can put your iPhone at risk but it proved to be the other way around as so far, your iPhone is more secured once it is jailbroken and the exploit has been patched.

We don’t know when Apple will release this software update, which will most likely come with 4.1. Apple usually isn’t quick to fix things up so if I had a guess I’d say we won’t see this update until the end of the month.